1. Field of the Invention
The present invention relates to a vehicle, such as an automobile, having an internal combustion engine, batteries powering electrical devices on the vehicle and an electrical connection box which is mounted on the vehicle, and also to electrical connection boxes for use in such a vehicle.
2. Description of the Related Art
Normally one secondary battery, e.g., rechargeable battery, having a rated voltage of 12V and a maximum nominal voltage of 14V is mounted on an internal combustion engine type automobile. A voltage up to the maximum voltage of 14V is applied from the battery to an internal circuit composed of bus bars and the like accommodated in the electrical connection box. The power supply is distributed by the internal circuit of the electrical connection box. The operation of electric/electronic component parts mounted on the vehicle is controlled through electric wires connected with the internal circuit.
In a goods vehicle, such as lorry or truck, a rated voltage of 24V and a maximum voltage of 28V are applied to a circuit, by a battery structure.
In recent years, electric/electronic component parts have been mounted in increasing numbers on a vehicle, and there is an increase in the electric current which is applied to each electric/electronic component part. For example, the electric power required to drive a fan is conventionally 130 watts, but has become 260 watts in recent years. At the rated voltage of 12V of the battery, it has become impossible to operate suction and exhaust devices of an engine, an electromotive power steering, and the like devices, requiring a high voltage such as 36V. Therefore, they are mechanically operated by the driving force of the engine.
With the increase of the electric current applied to each electric/electronic component part, the diameter of the electric wires used has become larger. Further, with rapid increase of the number of electric/electronic component parts, the number of electric wires has increased recently, which has increased the diameter of a wire harness including a bundle of electric wires. Consequently, the weight of the electric wires to be wired on a vehicle body has increased.
As described above, if the power supply from the battery is incapable of operating the suction and exhaust devices of the engine, they are mechanically operated. In this case, it is impossible to accomplish fine control of the operation of the suction and exhaust. Further, much fuel is consumed, which pollutes the environment. Accordingly, it is preferable to operate the suction and exhaust devices of the engine and the like not mechanically by a cam but electrically by the power supply from the battery.
In the case where the circuit is so constructed that a voltage higher than 14V can be applied to the circuit of the electrical connection box composed of bus bars and the like from the battery having the rated voltage of 12V and the maximum voltage of 14V, it is possible to reduce the required electric current and thus the diameter of the electric wires and the size of a bundle of a plurality of electric wires (e.g., wire harness). Therefore, it is possible to reduce the weight of the electric wires.
Further, with the application of a high voltage to the circuit composed of bus bars and the like, it is possible to control the operation of the suction and exhaust devices, the power steering motor, and the like not mechanically or hydraulically but electrically. In this case, it is possible to accomplish fine control of the operation of suction and exhaust devices and the like. Further, fuel consumption can be reduced, which reduces pollution.
It is preferable to apply a high voltage of about 42V to the electromotive power steering motor, the suction and exhaust devices of the engine, the fan, and other devices requiring a high voltage. On the other hand, in an automobile motorcar, it is preferable to apply the rated voltage of 12V (maximum voltage: 14V) to signal-generating devices of the electric/electrical components parts and coils of relays.
However, if the electrical connection box for distributing the power supply is provided with a circuit to which a low voltage up to the maximum voltage of 14V (28V in a truck) is applied and with a circuit to which a high voltage of about 42V is applied, a leak current is liable to be generated between the two circuits owing to the potential difference. Such a leak current may particularly occur if water or dirt enters the electrical connection box. The leak current is also liable to be generated in the circuit to which the high voltage of about 42V is applied.
It is an object of the present invention to prevent or reduce generation of a leak current in an electrical connection box, thereby permitting a circuit to which electric current having a low voltage is applied and a circuit to which electric current having a high voltage is applied.
According to the present invention, there is provided a vehicle having an internal combustion engine providing motive drive of the vehicle, a first, low-voltage battery structure including at least one secondary battery (rechargeable battery), and having a nominal maximum output voltage selected from 14V and 28V, a second, high-voltage battery structure including at least one secondary battery, and having a nominal maximum output voltage higher than that of the first battery structure and not more than 200V, a plurality of electrical devices powered by the first and second battery structures, and an electrical connection box containing an electrical circuit therein which effects connection between the first and second battery structures and the plurality of electrical devices.
The electrical circuit has an insulation plate and, fixed on one face of the insulation plate, at least one first bus bar (low voltage bus bar) connected to the first battery structure and at least one second bus bar (high voltage bus bar) connected to the second battery structure, whereby in operation the first and second bus bars are at different potentials.
In order to reduce a risk of electrical leakage paths on the insulation plate, at least one of the following features is present:
(i) the first bus bar or bars and the second bus bar or bars are separated on the face of the insulation plate by an air insulation zone containing no bus bars and having a width in a range of from about 1 mm to about 30 mm;
(ii) an insulation wall is upstanding from the face of the insulation plate between the first bus bar or bars and the second bus bar or bars; and
(iii) the second bus bar or bars are at least partially embedded in insulating material selected from synthetic resin and grease, while the first bus bar or bars are exposed on the face of the insulation plate.
When feature (i) is present, preferably a plurality of the second bus bars are located at a central region of the face of the insulation plate as seen in plan view while a plurality of the first bus bars are located at a peripheral region of the face as seen in plan view.
In another aspect, the invention provides an electrical connection box adapted for use in a vehicle which has a first low-voltage battery structure including at least one secondary battery and having a nominal maximum output voltage selected from 14V and 28V, and a second high-voltage battery structure including at least one secondary battery and having a nominal maximum output voltage higher than that of said first battery structure and not more than 200V.
The electrical connection box contains an electrical circuit having an insulation plate and, fixed on one face of the insulation plate, at least one first bus bar adapted to be connected in use to the first battery structure and at least one second bus bar adapted to be connected in use to the second battery structure, whereby in operation the first and second bus bars are at different potentials.
In order to reduce a risk of electrical leakage paths on the insulation plate, at least one of the following features is present:
(i) the first bus bar or bars and said the second bus bar or bars are separated on the face of the insulation plate by an air insulation zone containing no bus bars and having a width in the range of from about 1 mm to about 30 mm;
(ii) an insulation wall is upstanding from the face of the insulation plate between the first bus bar or bars and the second bus bar or bars; and
(iii) the second bus bar or bars are at least partially embedded in insulating material selected from synthetic resin and grease, while the first bus bar or bars are exposed on the face of the insulation plate.
When feature (i) described above is present, because the air insulation zone or area having the width of about 1 mm-about 30 mm is interposed between the respective regions of the low voltage bus bars, and the high voltage bus bars it is possible to prevent or minimize leak currents from being generated therebetween. As a result, the low-voltage bus bars and the high-voltage bus bars can be arranged on one insulation plate in the same layer. Therefore, it is unnecessary to place the low-voltage bus bars and the high-voltage bus bars in different and separate layers.
Accordingly, it is possible to reduce the size and thickness of the electrical connection box.
The number of the high-voltage bus bars is typically smaller than the number of the low-voltage bus bars. One or more high-voltage bus bars may be connected to one or more low-voltage bus bars through a relay mounted in the electrical connection box. As mentioned above, the high-voltage bus bars are preferably disposed in the center of the insulation plate and the low-voltage bus bars are disposed at the periphery around the high-voltage bus bars. Thereby it is possible to dispose the high-voltage bus bars to be connected to a fuse proximately to a relay connection tab to be connected to the low-voltage bus bar, which allows handling and mounting of the bus bars to be accomplished efficiently.
In the central region in which the high-voltage bus bars are disposed, adjacent high-voltage bus bars are preferably spaced apart by a distance in the range of from about 1 mm to about 30 mm, to avoid the risk that to leak currents are liable to be generated between the adjacent high-voltage bus bars.
When the feature (ii) described above is present, the height h and width w of the partition wall above the face of the insulation plate preferably satisfy the relations (1) and (2):
t less than hxe2x89xa720txe2x80x83xe2x80x83(1)
1.5 less than wxe2x89xa720sxe2x80x83xe2x80x83(2)
where t is the uniform thickness of the first and second bus bars and s is the maximum width of the first and second bus bars. The unit for h, w, t and s is all in mm. More preferably, w and h satisfy the relations (3) and (4):
t less than hxe2x89xa710txe2x80x83xe2x80x83(3)
1.5 less than wxe2x89xa710sxe2x80x83xe2x80x83(4)
In this case, a plurality of the first bus bars are preferably located in a first region of the face adjacent to a first one of opposite edges of the face, while a plurality of the second bus bars are located in a second region of the face which is spaced from the first region and is adjacent the other of said edges of said face.
Alternatively a plurality of the second bus bars may be located at a central region of the face of the insulation plate as seen in plan view while a plurality of the first bus bars are located at a peripheral region of the face as seen in plan view.
When feature (ii) described above is present, preferably an upstanding peripheral wall surrounds a region of the face of the insulation plate at which at least one second bus bar is located, and the insulating material is filled as a layer into a space bounded by the upstanding peripheral wall so as to cover and embed the second bus bar.
When feature (iii) is present, the insulating material is preferably selected from epoxy resin, two-part hardening resin and grease.
To fix the bus bars to the plate, a projection standing up from the insulation plate may be inserted into a hole formed on the bus bar and deformed (caulked) to fix the bus bar to a substrate resinous portion of the insulation plate.
It is preferably that the high voltage applied to the high-voltage bus bar or bars is 42V. In this case, it is easy to provide the voltage applied to the high-voltage bus bar to 42V by connecting in series three batteries each having a rated voltage of 12V (nominal maximum voltage: 14V) generally used in automobiles. Needless to say, it is possible to use a single battery having a maximum voltage of 42V. The reason why the high voltage to be applied to the high-voltage bus bar is set to 42V is partly because using a voltage close to or above 50V for the high-voltage bus bar may be more dangerous. The present inventors have conducted salt water experiments in order to ascertain the degree of the risk when applying a voltage of 42V in an electrical junction box suitable for use in an automobile engine compartment. A description of the experiments is as follows:
1 ml of salt water was injected into each terminal hole of the casing of a junction box which had bus bars disposed inside. Electrical components, such as relay, fuse, connectors etc., were mounted on the casing. A voltage of 42V was applied to bus bars of the junction box for 8 hours and suspended for 16 hours. This was repeated twice. There was initially no change to the bus bars and electrical components. However, after the third repetition, it was found that extra electric current passed between the bus bars, generating heat, and a portion of bus bars was melted. The heat also melted resin around bus bars such as an insulation plate, casing and resin portion of electrical components adjacent the casing.
Accordingly, it was confirmed that in consideration of normal use condition of an automobile, the application of the electric power at 42V to the electric/electronic component parts should not cause a problem.